How do you solve the quadratic equation by completing the square: #x^2 + 4x - 21 = 0#?
Your starting quadratic equation looks like this
To solve this quadratic by completing the square, you need to add a term to both sides of the equation, such that the left side of the equation becomes equivalent to the square of a binomial.
First, move the term that does not contain
To do that, you need to divide the coefficient of the
In your case, you have
Your quadratic will become
The left side of the equation can be wrtitten as
This means that you have
To solve this equation, take the square root from both sides of the equation to get
The two solutions for this equation are